By Dr Chris Mansell, Senior Scientific Writer on Terra Quantum
Below is a summary of some of the interesting research papers in quantum technology we’ve looked at over the past month.
Title: Scalable Multilayer Architecture of Single-Atomic Qubit Arrays Assembled in a Three-Dimensional Talbot Pincer Lattice
Organization: Darmstadt Technical University
In this paper, a novel way of fabricating large, configurable, and three-dimensional ultracold atomic arrays is described and realized. The method uses the Talbot effect, in which the refracted light has a certain intensity profile not only in the focal plane but also in several other planes. Atoms can then be trapped in the local extremes of this profile (maxima for red-detuned light or minima for blue-detuning). The system, as currently implemented, has 17 atom trapping planes, with more than 750 atom trapping sites per plane. This provides an opportunity to investigate large instances of quantum computing protocols because atoms can act as qubits that can be individually handled and made to interact with each other by pulling them into the Rydberg state.
Title: Race Track Trapped Ion Quantum Processor
Organization: Quantum; Honeywell Aerospace
In this paper, a new ion-trap design is presented. It is based on a device architecture coupled with a quantum charge but looks like an oval race track. It includes several components that allow it to be upgraded from its current size of 32 qubits. The researchers compared primitive operations and found that two-qubit logic gates were the dominant source of errors. They also investigate how different applications depend on different aspects of the system, using the performance of Hamiltonian simulations to assess two-qubit gate errors, QAOA algorithms to assess qubit connectivity, and dynamic repetition and simulation codes to assess mid-circuit measurements. and reset. Notably, the system achieved its highest quantum volume to date.
Title: Gap-free Bell lameness violation with superconducting circuits
Organization: ETH Zurich; Quside Technologies SL; Institute of Photonic Sciences; the Catalan Institute for Research and Advanced Studies; University of Paris-Saclay; Yale University; Sherbrooke University; Canadian Institute for Advanced Research
Until this landmark experiment, the only physical systems that had been used in the gap-free Bell test were nitrogen vaccum centers, optical photons, and neutral atoms. Superconductors have now been added to this list. This is important from a fundamental perspective because it is related to non-locality. The implications of technology are also thought provoking. Superconductors make up some of the world’s leading quantum processors and this experiment shows that they can be reliably linked using superconducting waveguides spanning tens of meters. This means they have the potential for use in device-independent quantum key distribution protocols and for distributed quantum computing.
Title: Solving Graph Problems Using Gaussian Boson Sampling
Organization: China University of Science and Technology; Chinese Academy of Sciences; New Foundation Science Laboratory
Identification of solid subgraphs is a problem that occurs in computational biology and finance. Providing acceleration over the classical approach to this problem is a possible application of Gaussian Boson Sampling, a non-universal quantum computation model in which Gaussian pinched states travel through a passive linear interferometer. This latest research extends previous Gaussian Boson Sampling experiments to a regime in which, to produce comparable results, today’s fastest supercomputers might need years to run their precise classical algorithms. Perhaps a faster classical algorithm could be developed but in the meantime, this is a very important development.
Title: Engaging Microwaves with Light
Organizations: Austrian Institute of Science and Technology; Vienna Center for Quantum Science and Technology
In this paper, microwaves are deterministically entangled with light having the wavelengths used by the telecommunications industry. This is important because it allows superconducting quantum processors to connect to shared networks. The result was achieved by placing a lithium niobate optical resonator in an ultra-low noise superconducting aluminum microwave cavity. Measurement of the square of the electromagnetic field was shown to violate the Duan-Simon separability criterion, thus verifying that entanglement was generated successfully.
Title: Cryogenic sensors enabling wide-band, traceable power measurements
Organizations: Aalto University; Bluefors Oy; IQM; Finnish VTT Technical Research Center; QTF Center of Excellence
Quantum electrodynamic circuits, in which superconductors interact with microwave photons, are one of the leading architectures for quantum computation. Increasing how well we can measure the strength of weak microwave signals would have very beneficial consequences for this setup. In this work, the researchers found a way to do this in a cryogenic environment over a wide frequency range. Compared with existing measurement devices, they increase the figure of the so-called noise equivalent power by two times and the thermal conductance of the important component more than five times. Their future experiments will involve using their device to calibrate microwave signals in experiments on superconducting qubits.
Title: Quantum Lock: The Provable Quantum Communication Excellence
Organization: University of Edinburgh; Sorbonne University; Indian Institute of Technology
Integrated circuits are physically unique because small random variations arise during the manufacturing process. Functions that cannot be physically cloned (PUF) use this fact to authenticate network devices, which is important for applications related to the Internet of Things. However, there is growing skepticism about their safety. In this paper, a hybrid PUF is envisioned in which the output of a classical PUF is encoded into a quantum state so that the indistinguishable properties of non-orthogonal quantum states can improve the security of the protocol.
Title: Towards the theoretical method of perturbation on quantum computers
Organizations: Purdue University; IBM
Perturbation theory allows physicists and chemists to use precise results from their understanding of simple quantum systems to estimate the eigenstates and eigenenergy of systems with additional interactions. In this paper, the authors design a quantum circuit that performs perturbation theory calculations. Applicable to various physical systems, they presented their method by considering the extended two-site Hubbard model and implementing their circuit on a 27-qubit quantum computer from IBM. Because certain aspects of computation can be performed in superposition, quantum circuits have the potential to outperform classical computation. Quantum circuits are very efficient because they don’t require any training or optimization.
Title: Studying the Multi-Body Hamiltonian with Heisenberg-Limited Scaling
Organizations: California Institute of Technology; University of California; Microsoft
Studying the unknown Hamiltonian parameters is an important task in quantum metrology, quantum computing, and the physics of many bodies. Algorithms that perform this task are often judged by how their runtime scales with the precision with which they learn the parameters. In this paper, an algorithm for many-qubit, local Hamiltonian is presented which runstime scales with the inverse of precision. This is known as Heisenberg limited scaling and is a significant improvement over the previous algorithm. This algorithm is also robust for expressing preparation and measurement errors. Since the runtime is independent of the number of qubits, the algorithm can scale to large system sizes.
Title: Algorithmic Quantum Acceleration Demonstration
Organization: University of Southern California
Artificial intelligence is unlikely to go beyond board games. Now, it’s having a tremendous impact on the world. This shows how useful gamified situations can be, as set out in this paper. It is an adaptation of the Bernstein-Vazirani problem where, after a single oracle invocation, the player tries to guess the string of hidden bits. If false, the hidden bit string is changed and the game repeats. When the oracle is quantum and there are no imperfections, the runtime scales with problem size better than when the oracle is classical. This is algorithmic quantum acceleration and does not depend on any guesswork or assumptions. Using dynamic decoupling on an IBM quantum computer, this acceleration was demonstrated over the entire range of problem sizes investigated.
May 29, 2023